Device providing differently colored illumination for microscopic objects



Nov. 8, 1932. P. KRAFT 1,887,099

DEVICE PROVIDING DIFFERENTLY COLORED ILLUMINATION FOR MICROSCOPIC OBJECTS Filed Maren-2o. 19:1

Invenlar Patented Nov 8, 1932 UNITED STATES PATENT OFFICE PAUL 1mm, 0] ma, 01mm, ASSIGNOB '10 THE m can Z3185, OI nun,

nnvroa rnovmnre panama! oonoann ILLUIINATION roa mcnosconc onmc'rs Application ma 1mm :0, mi, Serial He. seems, and in Germanyjarch 24.1930.

Transparent microscopic images, which cannot be distinctly seen in the microscope, are usually made visible b means of pigments. Setting aside this c emical coloring of the objects, which in most cases kills the living organisms, the suggestion has been made to use optical coloringmethods that do not influence the vitality of the objects and according to which a condenser with adjustable diaphra directs to the object pencils of illuminatmg rays which have re-.

.viously passed filters transparent to di erently colored light. Thewhole light pencil directed to the condenser was mostly -divid-- ed in a central and an exterior part, and the light of this exterior part was sometimes subdivided into several partial differently colored ray pencils allowing to alter their azimuth as well as their inclination relativecording to these suggestions could however satisf only moderate demands. The reason t erefore is that, with res ct to their effect, the light pencils of di erent colors have to be very finely toned relatively to each other so as to permit of obtaining a most favourable effect, which is superior to the ordinary dark field illumination with white light. "This toning which hitherto has not been sufiicientl taken intoconsideration varies with di erent inclinations of the ray pencils especially when a change is made between light field illumination, dark field illumination or a mixture of both.

The object of the present invention is to improve the optical coloring method. The invention consists in a device of the said kind for obtaining difierent chromatical effects in the, illumination of .microscopic objects,

which, according to the invention, has in the phra s, immediately in front of the second diap ragm, is provided a dispersin filter. The first diaphragm serves for reducing the intrinsic ,brilliancy of the illuminated dispersing filter and thesecond for reducing 5 the effective aperture of the dispersing filter. The central pencil of illuminating rags therefore takes the following way. T e first of the diaplhragms is illuminated by dispersed daylig t or by an artificial light on source. The pencil passing the diaphragm aperture is diverging and this also in the case of an artificial light source disposed approximatel in the focus of an illuminat1on lens. T e diver ence of the pencil is 5 based u on the fact that the artificial light sources ave practically always a certain extension, that is to say that they are not exactly punctifo'rm, and that a frosted disc, which as a rule acts as a divergin filter, is disposed behind the light source. rovided the two diaphragms are given a suitable mutual distance, the diverging 'filter lying immediately in front of the second diaphragm, owing to the divergence, is uniforml illuminated over its whole extension wit an intrinsic brillianc which depends on the aperture of the rst diaphragm, but also approximately uniformly when the diaphragm aperture is narrow. The diverging filter acts as the real light source for the central pencil; its aperture is constricted by narrowin down the aperture diameter of the secon diaphragm lying near it. Using 7 only this second diaphragm instead of both diaphragms is not admissible with a somewhat bright light source because the sometimes necessary use of a very narrow diaphragm aperture might allow difiractions of the light and thus impair the quality of the image in the microscope. On the other hand, a device in which the first diaphragm is replaced by a fumed glass or the like which, together with the second diaphragm, influences the central partial pencil in the sense of weakening the light would not al low of obtaining sufliciently brilliant images. The pencil passes invthis case the central color filter in'order to be finally directed by the condenser to the object.

Contrary thereto, the exterior pencil of illuminating rays passes directly the color filter provided in its ray path; for regulating its brilliancy serves the diaphragm disposed at the condenser. By stopping down the pencil from the exterior edge this diaphragm acts in the case of catoptric condensers with an even number of reflexions and in the case of dioptric condensers as an aperture diaphragm, whereas for example with the paraboloid condenser which reflects the rays only once it only reduces the intrinsic brilliancy by stopping down the leaving pencil from the central edge.

The device can be further improved by making the light transparenc of the color filters variable by exchangea le additional filters of fumed glass'or the like.

The accompanying drawing shows a constructional example of the invention in a central section in front elevation.

In the condenser support a of any microscope is inserted in the well-known manner a two-lens light field condenser 17. For constricting its aperture this condenser 15 is provided with an iris diaphragm whose diaphragm aperture can be altered by means of a lever (Z. At the lower side of'the condenser support a a filter supportv f is pivotally provided by means of a screw 0. In the filter support f are inserted a ring-shaped red filter g and a smoked glass it of equal size. The ring aperture of these light filters comprises a tube 2' which can be fixed by means of a threaded ring 70 which serves at the same time as a mount for a blue filter l.

Directly beneath the blue filter Z, in the tube 2', is disposed an iris diaphragm m which can be adjusted by means of a lever 11. and whose diaphragm plane is closely above a' dispersing filter o of frosted glass absorbing the ultraviolet rays. At the lower end of the tube 2' is'an iris diaphragm p having an adjusting lever g. If required, also the cen' tral color filter Z may be supplemented by an additional fumed glass filter 1'.

When using the device care must be taken that those light rays which pass the two filters g and 71. leave the condenser 12 with such an inclination relative to the condenser axis that they pass outside the front lens of thejust used microscope objective and that here only light diffracted in the object is allowed to pass. However, if the inclination of part of these leaving rays is too slight, the corresponding part of the pencil is to be stopped down by exchanging the threaded ring is for a ring having a bigger flange or by stopping the light down by placing on the threaded ring sponding size. As soon as this condition is met, and when the axes of the tube i and the condenser 12 coincide, the light filtered in the parts 9 and k is sure to produce only a pure dark field illumination of the object, the

k a diaphragm ring of correbrilliancy of which can be altered by exchanging the fumed glass ring it for a ring of another transparency and by adjusting the stop 0 by means of the lever d.

Those illuminating rays which pass the blue filter Z leave the condenser 6 under such inclinations relative to the optical axis of this condenser which do not prevent their-entrance into the front lens of'any microscope objective. \Vhon the axes of the tube i and the condenser b coincide, the light filtered in the part Z provides a light field illumination of the object. The free apertures of the diaphraglns m and p are altered by adjusting the lovers n and g, and the light field illumination is thus toned relatively to the dark field illumination, which is producedby the exterior pencil of illuminating rays,

in such a manner that the just used light source provides the most favorable illumination of the object. Also in the case of a very brilliant light source emitting a great quan-- tity of ultraviolet rays, owing to the light being strongly subdued by the diaphragms m and p and to the absorbing efi'ect of the dispersing filter 0, the observer need not fear any detrimental effect when having to work with the illumination device during a protracted period.

If so required, the filters g and Z may be substituted also by such filters which are transparent for different colors in different azimuths. In this case the azimuth of the different colors can be altered by turning the tube z, and the filters g and Z, about its axis in the filter support f. Observations can be made also with oblique illumination when the filter support f'is turned out of the position shown in the drawing about the screw bolt 0 over a certain angle.

I claim: 1

- 1. A device providing diflerently colored illumination for microscopic objects, comprising a condenser, a diaphragm with adj ustable aperture connected to the condenser, a color filter disposed in theexterior part of the condenser aperture, :1. color filterof dif- 

